Composites of filled thermoplastic compositions with sound deadening properties are well known for use in automotive applications. The thermoplastic compositions typically comprise a polymer, a plasticizer and a filler. A number of patents have been granted for such highly filled thermoplastic compositions as represented by U.S. Pat. Nos. 4,191,798; 4,222,924; 4,263,196; 4,379,190; 4,403,007; 4,430,468; 4,434,258; and 4,438,228. Different systems of polymers, plasticizers and fillers have been proposed for sound deadening applications in automotive flooring. For example, the above-mentioned patents disclose the use of ethylene interpolymers such as ethylene/vinyl ester, ethylene/unsaturated mono- or di-carboxylic acids, or esters of unsaturated acids, etc. Blends of such ethylene interpolymers with other elastomers and polymers have also been proposed in these applications. Further, various filled polyethylene copolymer, polyvinyl chloride, ethylene-propylene-diene compositions are used for applications in wire and cable.
Notwithstanding the proposal of many different polymer based filled compositions for use in sound-deadening composites and other applications, ethylene vinyl acetate (EVA) has been most widely used on a commercial basis. There is practical limit for addition of fillers such as the more commonly employed medium-density fillers, e.g., CaCO3, bauxite, gypsum, etc. As the filler levels rise above a certain point, other properties suffer, such as melt index (as it drops, extruder pressures mount rapidly), softness (the “hand” becomes much stiffer), and elongation (which drops alarmingly). Ultimately, it is not possible to compound binary EVA/CaCO3 blends as the mixture will no longer “flux” in a Banbury Mixer (the charge merely stirs—the resin will not “work” as the blades turn, no power rise ensues, the mixture on discharge is still discrete EVA pellets in a powdery Whiting mass). If one were to use a very dense filler, such as BaSO4, slightly more filler can be added to binary EVA blends. However, there is a demand for improved materials which meet a number of balanced properties such as impact strength, tensile, elongation, flex modulus, heat resistance and specific gravity. In addition, where the sound-deadening composition or composite is used in certain applications such as automotive flooring, a number of other requirements have been specified by automobile manufacturers. For example, automotive materials or parts must satisfy requirements of resistance to cold, mildew, fogging and flammability.
Thus, there is a need for other materials that have improved noise, vibration and harshness dampening properties, increased heat resistance, and low modulus for use in flooring for automotive, cable and wire and roofing members.